FI63426C - FOER REFRIGERATION AV CONTAINER AND ENVIRONMENTAL POLYMER LEVER - Google Patents

Description

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Patent and other registration AmMuii utiagd och uti.ikrtft * n public · rad (32) (33) (31) Pyy4 «t * y utueiiceui — aegird prieritet 19.07.77 Australia-Australien (AU) PD. 0903 (71) Dulux Australia Ltd, 1 Nicholson Street, Melbourne, Victoria, Australia-Australia (AU) (72) Willy Braun, East Brighton, Victoria, Australia-Australia (AU) (74) Oy Kolster Ab (5 ^) The present invention relates to a process for removing water from an aqueous slurry of polymeric beads containing a polyvinyl alcohol dispersion stabilizer to obtain polymeric beads as a soft, brittle cake. Furfarande för awattning av en vattenuppslamning av polymer pärlor

In recent years, it has been proposed to use polymer beads, for example synthetic polymer and granules with a diameter of 1 to 50 microns, as opacifiers and opacifiers in products such as paints, plastics and paper.

One particularly useful type of bead is obtained from an unsaturated polyester resin which has been cured by crosslinking it with styrene or a similar unsaturated monomer. The beads may be solid or porous and typical examples are described, for example, in Australian Patents AU 434,658 and 439,432.

Beads of this type are generally prepared by a process to obtain an aqueous slurry of polymeric beads containing poly (vinyl alcohol) as a dispersion stabilizer. The process is described in 63426, for example in Australian Patent AU 445 277. The bead content of the sludges is generally about 30% by weight.

When such polymeric beads are to be used in an aqueous product, for example a latex paint, they can often be mixed directly as an aqueous slurry with other components without intermediate dewatering treatment. However, if the final product has to be substantially anhydrous, the required removal of water from the beads prepared as an aqueous slurry can cause serious economic and technical problems.

For example, the energy required to dry the 30% by weight aqueous slurry of the beads by direct evaporation in a reasonable time can cause a significant cost increase. In addition, it has been found that heating the slurry to evaporate water can cause the formation of hard bead aggregates. Decomposition of these aggregates in a subsequent dispersion process can be difficult or even impossible. This problem appears to be due to the presence of a poly (vinyl alcohol) dispersion stabilizer in the slurry.

Concentration of the slurry by precipitation or centrifugation to remove most of the water does not appear to be a suitable alternative to evaporative drying, as the density of the beads is often too close to the density of water for efficient separation. Attempts to filter pearls from sludge have also failed. The beads, which are spherical in shape, quickly pack into a dense cake which, in the presence of poly (vinyl alcohol), clogs the filtration layer and reduces the permeation rates to too low. Although cakes have been made by these methods, it has been found that drying the cake, for example by hot air flow, still results in the formation of hard, unacceptable aggregates.

It has now been found that if an aqueous slurry of polymer beads containing a poly (vinyl alcohol) dispersion stabilizer is first destabilized as described below, the slurry can be dehydrated by conventional means and result in a soft, stabilizer-free cake. The cake can then be dried to a brittle, redispersible powder if desired.

The present invention relates to a process for removing water from an aqueous slurry of polymeric beads containing a poly (vinyl alcohol) dispersion stabilizer, which process is characterized in that 63426 (1) is an insoluble organic destabilizing agent having a molecular weight of at least 200 and a carboxylic acid or heavy metal salt thereof. a derivatized acid-containing substance or amine is precipitated from a slurry-soluble parent compound containing solubilizing ionizable groups to flocculate the slurry and promote dewatering from the slurry, and (2) physically separating the water from the slurry , which is substantially free of poly (vinyl alcohol) dispersion stabilizer.

The separation of water in step (2) can be performed by conventional physical means, for example, by filtration or centrifugation to obtain a soft, substantially stabilizer-free polymer cake with some residual water. If necessary, this cake can then be dried, for example, by circulating hot air over or through the cake at a temperature lower than the softening point of the polymer beads.

The dual effect of the destabilizing agent used is somewhat surprising, given that a few other well-known agents, specifically certain polymeric flocculants used in water treatment processes, flocculate such polymeric bead slurries but do not destabilize them to the extent that water can be easily removed. It seems that flocculation of the beads alone does not solve the dewatering problem.

In the process according to the invention, the destabilizing agent is precipitated in the slurry, the destabilizing agent itself being insoluble in the aqueous phase of the slurry and can be produced in situ from a soluble parent compound.

The destabilizing agents used in the process are organic substances, which may or may not be polymeric. However, they must have a molecular weight of at least 200. In their soluble form, destabilizing agents contain solubilizable ionizable groups, the elimination of which renders the molecule as a whole insoluble in the aqueous phase of the slurry.

Suitable carboxylic acids for use as destabilizing agents include, for example, stearic acid, 12-hydroxystearic acid, abietic acid, oleic acid and dimerized fatty acids, styrene / maleic anhydride copolymer, diisobutylene / maleic anhydride copolymer and 4-maleic anhydride copolymer. It has been found that for best results, the carboxylic acid should have an acid number of at least 100 mg KOH per g. Other preferred destabilizing agents are the heavy metal salts of these fatty acids.

Suitable destabilizing agents containing acid groups derived from sulfuric or phosphoric acid include, for example, sulfonated polystyrene and sulfated castor oil. Also useful are substances prepared, for example, by sulfonation of the maleic anhydride half ester of a styrene-allyl alcohol copolymer to give a polymeric product that is soluble in alkali but becomes insoluble in water upon acidification. A somewhat similar class of destabilizing agents can be prepared by reacting a polymer or copolymer of glycidyl methacrylate with sulfuric or phosphoric acid.

Alternatively, the insoluble destabilizing agent may be an amine. As in the case of acidic destabilizing agents, the amine itself must be insoluble in the aqueous phase of the bead slurry.

The carbon chain of the primary amine may be a fatty acid group derived from, for example, lauric acid, myristic acid, stearic acid or oleic acid, or mixtures of these acids when derived from natural products. Suitable destabilizing agents of this type include tallow, coconut and soy amines.

The carbon chains of the secondary amine may consist of the groups mentioned above. Alternatively, the molecule may contain both primary and secondary amine groups.

Suitable diamines are, for example, oleylpropylene and laurylpropylene diamine and their fatty acid salts, for example the mono- or dioleyl salt. We have found that, for example, the mono-fatty acid salt of oleylpropylenediamine is a particularly useful destabilizing agent for certain bead slurries.

The amine may be an amphoteric ion (zwitterion), for example it may be a compound having the structure:

R-NH-CH-CH - C-OH

I ^ I! CH3 o wherein R is an alkyl group, for example a lauryl chain.

The form of the destabilizing agent when added to the slurry as a soluble derivative naturally depends on the composition of the destabilizing agent itself. For example, the acidic destabilizing agent can be converted to a water-soluble sodium or potassium salt of 63426 by reaction with the corresponding base and reprecipitated, if necessary, by acidifying the slurry. Alternatively, a suitable soluble acid may be reacted with a heavy metal salt, for example barium chloride and calcium nitrate, to precipitate the acid heavy metal salt.

A suitable way to form an amine destabilizing agent in a slurry is to start with the corresponding soluble alkyl acid salt and form an insoluble destabilizing agent therefrom by an exchange reaction with, for example, an alkali metal fatty acid soap. For example, soluble oleylpropenediamine diacetate reacts with sodium stearate to precipitate the corresponding insoluble stearyl destabilizing agent.

When the amine is an amphoteric ion, it can be solubilized, like the acidic destabilizing agents described above, by converting it to an alkali metal salt, for example, by reacting sodium hydroxide with a carboxyl group. The destabilizing agent is then formed in situ in the slurry, where the salt is dissolved by acidifying the aqueous phase of the slurry.

When selecting a destabilizing agent, it is, of course, necessary to select an agent that does not adversely react with any component of the slurry being treated. For example, it has been found that if the slurry contains small amounts of benzoic acid, e.g. as a residue from the benzoyl peroxide polymerization initiator formed during bead preparation, these may react with aliphatic amines, which would therefore not be suitable destabilizing agents for use with this slurry.

The amount of destabilizing agent used depends on factors such as the concentration of poly (vinyl alcohol) in the slurry and the chemical nature and size of the polymeric resins.

It is therefore usually advisable to experimentally determine the optimum concentration for a particular combination of slurry and destabilizing agent. However, it has been found that a concentration of 1 to 3% by weight, based on the dispersion phase of the slurry, is usually sufficient. At lower concentrations, the rate of dewatering is slowed by incomplete flocculation of the beads, and at much higher concentrations, no benefit is usually achieved.

If the destabilized slurry is not already at a temperature of at least 50 ° C, it must be heated to this temperature to complete the process before it is concentrated by filtration or centrifugation. The final cake can be easily washed with water to remove small amounts of residual poly (vinyl alcohol) stabilizer. The final cake has a solids content of typically 60-70% by weight, excluding any water that may be present in the internal occlusions of the dispersed particles.

Provided that, as mentioned above, the softening point of the polymeric melts is properly taken into account, the soft cake obtained in the dewatering process can be dried by conventional means.

The invention is explained in the following by means of examples in which all amounts are given in parts by weight.

Example 1

Use of a polycarboxylic acid destabilizing agent in the filtration of a polyester bead slurry The polyester bead slurry used in this example had the following properties. The beads were unsaturated polyester resin cured by reaction with 40% by weight styrene monomer. The slurry contained 38.9% by weight of beads with a maximum diameter of 50 μm and an average diameter of 20-25 μm, dispersed in an aqueous phase containing 2.4% by weight of poly (vinyl alcohol) based on the weight of the beads present. The quality of the poly (vinyl alcohol) used was 88% hydrolyzed poly (vinyl acetate) having a viscosity of 40 cP at 20 ° C as a 4% by weight solution in water.

To 2604 parts of a slurry (containing 1000 parts of beads) was added 700 parts of water and the pH was adjusted to 7.5-8.5 with ammonia solution.

A solution of the soluble ionizable polycarboxylic acid salt was prepared by dissolving 33% by weight of a copolymer of styrene and maleic anhydride in alkaline water with ammonia in a molar ratio of about 52:48. The copolymer had a molecular weight of about 2,500.

Thirty parts of ionizable brine was diluted to 500 parts with water and added to the slurry with stirring. The pH was adjusted to 4.5 with a 10% by weight aqueous solution of acetic acid to release the polycarboxylic acid destabilizing agent, and the batch temperature was raised to 70 ° C. The sample was examined under a transmission microscope at 200x magnification and the slurry was found to be well flocculated.

The cartridge was easily filtered through a conventional vacuum filter.

7 63426

The filter cake was washed with water to give a clean, brittle product.

The initial filtrate was remarkably viscous and gelled upon addition of sodium borate in a manner characteristic of a poly (vinyl alcohol) solution.

A sample of the untreated slurry showed no flocculation when viewed under a microscope. Attempts to filter it through the same vacuum filter used for the destabilized slurry failed even when the sample was heated to 70 ° C and diluted with additional water.

Clogging of the filter media with the pearl cake quickly reduced the filtration rate to impractical seepage.

Example 2

Use of fatty acid destabilizing agent

The treatment of Example 1 was repeated except that 30 parts of ionizable saline was replaced with 600 parts of a 5% by weight solution of sodium stearate in hot water.

The destabilized slurry was again easily filtered and poly (vinyl alcohol) was detected in the filtrate.

Similar results were obtained using sodium dodecyl benzenesulfonate instead of sodium stearate and acidifying to pH 2 with hydrochloric acid instead of acetic acid. The slurry was stable at pH 2 in the absence of sodium dodecylbenzenesulfonate.

Example 3

Use of a heavy metal salt destabilizing agent A sample of 2604 parts of polyester bead slurry adjusted to pH 8.9 was prepared as in Example 1.

Then, 600 parts of a 5% by weight solution of sodium stearate in hot water was added to the slurry with constant stirring, followed by the addition of 110 parts by weight of a 5% by weight aqueous solution of calcium chloride. In the presence of the heavy metal salt stabilizer thus formed, the beads were found to flocculate.

The batch was then heated to 70 ° C and filtered as described in Example 1. Again, good filtration rates were achieved. The washed filter cake was soft and brittle. Poly (vinyl alcohol) was again detected in the filtrate.

Example 4

Use of an aliphatic primary amine as a destabilizing agent A sample comprising 2604 parts of polyester bead slurry adjusted to pH 7.5-8.5 was prepared as in Example 1.

63426 600 parts of an acetate salt solution of the primary amine derived from 5% by weight of coconut fatty acid in water were added with stirring to the slurry. The pH was then adjusted to 9.0 with 5% by weight aqueous sodium hydroxide to precipitate an aliphatic primary amine destabilizing agent. Microscopic examination of the slurry confirmed that the polyester beads were flocculated when germinated.

When heated to 70 ° C, the batch was easily filtered with the desired results as in Example 1.

Example 5

Use of a fatty acid salt of a diamine as a destabilizing agent

The molecule contains both primary and secondary amine groups.

A sample of 2604 parts of polyester bead slurry adjusted to pH 7.5-8.5 was prepared as in Example 1.

360 parts of a 5% by weight aqueous solution of tallow trimethylenediamine diacetate salt were added with stirring to the slurry, followed by the addition of 200 parts of a 5% by weight solution of sodium stearate in hot water and heating the charge to 70 ° C.

In the presence of the destabilizing agent formed in situ, the polyester beads were well flocculated.

Preferred results similar to those in Example 1 were obtained when the slurry was filtered as described in said example.

When this example was repeated sequentially using coconut, soy and olive trimethylenediamines as the base for fatty acid salt destabilizing agents, satisfactory filtration rates and filtration cakes were obtained.

The filter cakes were allowed to dry at 70 ° C in a stream of warm air to give free flowing powders that were substantially free of bead agglomerates.

Example 6 Effect of temperature on the filtration rate of a destabilized bead slurry containing poly (vinyl alcohol) The beads used in this example were similar to Example 1 except that the bead content was 37% by weight of the slurry.

To 1350 parts of bead slurry (500 parts of beads) was added 350 parts of water and the pH was adjusted to 8-9 with aqueous ammonia solution.

63426

Three hundred parts of a 5% aqueous solution of sodium stearate was then added with stirring to the batch, after which the pH was adjusted to 4-5 with 10% by weight aqueous acetic acid.

The beads flocculated.

The batch was then subjected to filtration experiments according to Example 1 but using treatment temperatures that did not exceed the temperature at which poly (vinyl alcohol) precipitates from aqueous solution. The time required to filter equal parts of the slurry at different temperatures and the appearance of the filtrate are given in the following table.

Filtration temperature ° C_Time__Filter_ 30 7 h milky 50 1 h 20 min. slightly dull 70 11 min. cloudy 80 8 min. bright

The results show that complete destabilization is not achieved at temperatures below 50 ° C, at which temperature and above which there is a substantial increase in the filter permeation rate.

Although slight migration of very small beads was observed at 50 ° C, which became less noticeable as the temperature continued to rise, we found that the destabilization efficiency and filtration rate are acceptable provided that the minimum temperature was maintained.

Similar results were observed when the experiments were repeated using the stearate salt of thalitrimethylenediamine as a destabilizing agent.

Example 7

Comparison using conventional coagulants as filtration aids

Attempts were made to use conventional, commercially available, high molecular weight polyelectrolyte coagulants as destabilizing agents for the slurry of Example 1, using the filtration method described in said example.

The selected substances were products sold under the trademark "Alfloc" as flocculants for use in industrial water clarification processes. The quality grades used had the following characteristics: 10 63426

Class_Charge in solution_0.1% pH of the solution

6701 nonionic about 7.0 6751 anionic about 7.8 6361 cationic 5.0-5.5

Each flocculant was prepared as an aqueous solution and added to a sample of the slurry used in Example 1, at the concentration recommended by the substance manufacturer. In each case, flocculation of the beads was observed under a microscope, but the filtration rates were extremely slow and the filtrates were quite opaque. The filter cake had a dense appearance and retained a substantial portion of the poly (vinyl alcohol) used as a slurry stabilizer.

These results, when compared to those obtained using the destabilizing agent of Example 1, indicate that flocculation of the bead slurry alone is not sufficient to de-stabilize the slurry and release poly (vinyl alcohol) into the filtrate.

Example 8

Use of destabilizing agents containing sulfuric acid groups

A slurry of 40% by weight of cross-linked polyester beads with an average diameter of 35 μm in the aqueous phase containing 2.5% by weight of poly (vinyl alcohol) stabilizer was destabilized as follows.

To 2500 parts of a slurry containing 1000 parts of beads was added 700 parts of water with stirring. The pH was then adjusted to 7 with aqueous sodium hydroxide solution and the temperature was raised to 70 ° C. 60 parts of a 50% by weight aqueous solution of the sodium salt of sulfated castor oil ("Turkey Red Oil") were added.

Acetic acid was then added until the pH reached 3.2. A slurry sample examined under a microscope showed that the beads, which had previously been well dispersed, had become very highly flocculated. The destabilized slurry was easily filtered through a vacuum filter. The filtrate contained poly (vinyl alcohol).

The procedure described above was repeated with equal results using a slurry containing 32% by weight of polyester beads with an average diameter of 10 yarns. The slurry could not be filtered at an acceptable rate prior to destabilization according to this invention.

In the same manner, a slurry containing 35% by weight of polyester beads with an average diameter of 15 μm was destabilized and filtered.

Claims (5)

A method for removing water from an aqueous slurry of polymer beads containing a poly (vinyl alcohol) dispersion stabilizer, characterized in that (1) an insoluble organic destabilizing agent having a molecular weight of at least 200 and a carboxylic acid or its heavy metal salt derived from sulfuric or phosphoric acid a group-containing substance or amine is precipitated from a slurry-soluble parent compound containing solubilizing ionizable groups to flocculate the slurry and promote dewatering from the slurry, and (2) the water is removed from the slurry by physically separating at a temperature of at least 50 ° C substantially free of poly (vinyl alcohol) dispersion stabilizer. Process according to Claim 1, characterized in that the soft cake formed from polymer beads is dried to a brittle, redispersible powder. Process according to Claim 1, characterized in that the insoluble destabilizing agent is a carboxylic acid having an acid number of at least 100 mg KOH / g. Process according to Claim 1, characterized in that the insoluble destabilizing agent is a primary amine of the formula R-NH 2, a secondary amine of the formula R-NH-R or a diamine of the formula R-NH-R 1 -NH 2, in which R and R 1 are alkyl groups and the length of the carbon chain in R is 12 to 18 atoms. Process according to Claim 4, characterized in that the amine is an amphoteric ion.